Novel cardo poly(arylene ether sulfone)s with pendant sulfonated aliphatic side chains for proton exchange membranes

Novel cardo poly(arylene ether sulfone)s containing pendant sulfonated aliphatic side chains were successfully prepared by convenient nucleophilic substitution polycondensation and sulfoakylation reaction. Cardo poly(arylene ether sulfone)s with amide groups were prepared by polymerization of 3,3-bis(4-hydroxyphenyl)-1-isobenzopyrrolidone and 4,4′-difluorodiphenylsulfone or 3,3′,4,4′-tetrafluorodiphenylsulfone, which then reacted with various sulfoalkylating agents to introduce different length sulfonated side chains in a mild reaction condition. The content, location and length of the side chains were exactly controlled. All the polymers were thoroughly characterized by FT-IR and 1H NMR spectroscopy. Tough and flexible membranes of the polymers with good mechanical properties and stability were obtained from solution casting in NMP. The membranes displayed low water uptake and swelling ratio both at ambient temperature and elevated temperatures, as well as appropriate proton conductivity compared to Nafion 117. Much lower methanol permeability in the range of 10−7 cm2 s−1 and higher selectivity about 105 S s cm−3 compared to Nafion 117 were also observed for these novel sulfonated polymers. The influences of different length side chains and fluorine groups on the properties of sulfonated polymers were also discussed. With these properties, the new sulfonated poly(arylene ether sulfone)s seem to be promising polyelectrolyte materials for proton exchange membrane fuel cells.